Dental engine.



No. 863,478. PATENTED AUG. 13, 1907.

W. W." WILLIAMSON.

DENTAL ENGINE. APPLIOATION FILED JAN 7 1907 2 SHEETS-SHEET 1.

m VEJVIOR ZJ N RS co., vusnmcrou, n. c.

No. 863,478. PATENTED AUG. 13, 1907. W. W. WILLIAMSON.

DENTAL ENGINE; APPLIUATION 2mm 1.5.x. 7. 1907.

2 SHBETS-SHEET 2.

.HTTORJVE Y. 1 10 rnruonms PETERS 00., wnsnnvcrou, n cy WALLACE W. WILLIAMSON, OF SYRACUSE, NEW YORK.

DENTAL ENGINE Specification of Letters Patent.

Patented Aug. 13, 1907.

Application filed January '7, 1907. Serial No. 351.135.

To all whom it may concern:

Be it known that I, WALLACE W. WILLIAMSON, a citizen of the United States, and a resident of Syracuse, in the county of Onondaga, in the State of New York, have invented new and useiul Improvements in Den tal Engines. of which the following, taken in connection with the accompanying drawings, is a full, clear, and exact description.

This invention relates to the class of dental-engines comprising an electric-motor and mechanism driven thereby for transmitting the power to the various kinds of instruments used by dentists.

The chief object of the present invention is to produce a dental-engine of that character wherein the power-transniitting mechanism shall permit of regulation so as to cause the instrument to be driven at different speeds as may be desired, and to provide simple and convenient manually-operated means for either changing the speed of the transmission mechanism or throwing the said mechanism into and out of operative relation with the motor, and furthermore to provide the motor-supply circuit with simple and reliable cir cuit-making and breaking devices controlled by the manually-operated means whereby the circuit will be closed when the transmission-mechanism is thrown into operative condition, and opened when the said mechanism is thrown out of operative condition.

Another object of the invention is to produce a dentalengine which shall permit the motor and powertransmitting mechanism to be located quite remote from the manually-operated device for-controlling the said mechanism and aforesaid circuit-making and breaking means, said manually-operated devices being designed to be placed in a convenient position upon the floor adjacent to the dental-instrument.

To that end the invention consists in the novel construction and arrangement of the component parts of the power-transmission mechanism and electric-circuit-making and breaking devices, in combination with a motor, and the novel arrangement of the foot-operated means for controlling said mechanism and circuit-making and breaking devices as hereinafter fullydcscribed and set forth in the claims.

In the accompanying drawings, Figure l. is a front view ot' the dental-engine embodying my invention; Fig. 2 is a side view of the same; Fig. 3 is a plan view; Fig. 4 is an enlarged vertical section taken on the line XX in Fig. 1; Fig. 5 is an enlarged detail view of the electric-eircuit-making and breaking switch and means for actuating the same; Fig. (i is a sectional view of said switch taken on the line -YY in Fig. 5 and showing more clearly the electric connections and insulated contacts; Fig. 7 is a detail face view of the stationary contact adapted to be engaged by the contact of the switch; Fig. 8 is an enlarged section of the lootopcrated device for controlling the power-transmission mechanism and circuit-making and breaking switch and taken on the line *ZZ in Fig. 2; Fig. 9 is a detail inverted plan view of the disk; and Fig. 10 is a detail plan View of the plate which is designed to be secured to a floor and to which the aforesaid disk is pivotally connected Similar numerals of reference indicate corresponding parts:

1 represents an electric-motor having the usual inclosing-case and 22 denote the wires of a suitable supply-circuit. The motor-case is provided with a plate 3 for fastening the same to a wall or other suitable support indicated at 4 in Figs. 2 and 3 of the drawings.

The shaft 5 of the motor is preferably disposed upright and has its upper end protruding from the inclosing-case, and to said end is rigidly fastened a horizontal disk -6 arranged concentric to the shaft and formed with a central depression 7 in its upper lace as clearly shown in Fig. l of the drawings.

Upon the motor-case is suitably mounted a bracket comprising two upwardly extending arms -8-8 provided with coinciding bearings 9-9- disposed in horizontal alinement, in which bearings is supported an irrevoluble longitudinally-shit'tal)le shalt l.0 extending diametrically over the disk 6. On said shalt is journaled a wheel 1l. which is held from moving endwise ol' the shalt by means of collars l2-l2- secured to the said shalt. Said wheel is adapted to be l'rictionally driven by the disk -t3- and is formed with a groove Ul-- in which runs a belt -l4 designed to transmit the power from said wheel to the dentalinstrument (not shown).

To one end of the shaft l0- is secured a collar -l5 and between said collar and adjacent bracketarm 8 and surrounding the shalt is a spiral-spring -l(i serving to move the said shaft. in one direction to maintain the wheel lnormally over the depression 7-- in the disk oand thus out of contact with said disk as shown in Figs. 1. and 1 ot the drawings. This movement of the shaft is limited by means of a stop-collar *l7 fastened to the shaft and adapted to engage the other bnu-ket-rmn *S as shown in Figs. 1. and 5.

To the end of the shalt, adjacent to the stopwollar, is pivot-ally connected one end of a rod ts which has its opposite end pivotally connected to the upper end of an upright arm -l 9- which is rigidly secured at its lower end to a rock-shalt. -2() disposed below the shalt l0 and at right angles thereto. Said rockshalt is journaled in a sleeve 2l formed on the bracketarm -8 \djacent to the sleeve -Zl-, the bracket-arm S is l'ormed with a depending-arm 22 and on this arm is supported a segmental electriccont'act plate '23 arranged concentric with the axis of the rock-shalt 20. Said contact-plate is preferably fastened to the front side of the arm -22 by means of a screw -24 which passes through the arm and has one end entering the plate and the opposite end entering a binding-post 25 disposed at the rear side of the arm, to which binding-post is connected the wire 2- of the electric-circuit.

The contact-plate 23 is insulated from its support as indicated at 26-, and the attaching-screw 2L passes through an aperture 27 in the arm which is of suilicient size to prevent an electriccontact between the arm and screw, which latter forms part of the electric-circuit as clearly shown in Fig. 6 of the drawings. The said contact-plate is provided with a block of insulating material 2S which is preferably set in the plate substantially at the center of its length as shown in Fig. 7.

29 denotes a circuit-making and breaking switch which consists of a depending bar secured at its upper end to the aforesaid rockshaft 20 and is provided at its lower end with an electric-contact 30 adapted to move over the contact-plate -23. The contact 30- consists preferably of a pin fastened to a bindingpost -31 carried on the switch and insulated therefrom as indicated at 32-. To said binding-post is connected the wire -2 of the electric-circuit as clearly shown in Fig. 6.

It is obvious that the conducting-wire 2 is cut to permit the same to be attached to the two binding-posts 25 and 3 l.

To the rock-shaft 20 is also secured a grooved wheel -33 operative for turning the shaft in one direction for the purpose hereinafter explained.

3ldenotes a disk which is provided with circumferential groove -34 and is pivotall y connected to an annular plate 35- fastened by means of screws 36 to the floor of the room or apartment in which the dental-instrument is to be used. The disk -34 is connected to the wheel 33 by means of a belt 37 which is connected to the disk as indicated at 35 and runs on a pair of pulleys 3838 mounted on a plate 39 designed to be fastened to a wall or other support disposed substantially in a plane with the wheel 33 and also running on a pair of pulleys 4040 mounted on brackets 4l11 secured to the wall near the floor as clearly shown in Figs. 1, 2 and 3 of the drawings. The said disk 34 is formed with radially extending arms 4242 serving as levers to permit the same to be operated by the foot of the person using the dental-instrument, for the purpose of controlling the power-transmitting mechanism and circuit-making and breaking switch. I prefer to pivotally connect the disk 34- to the floor-plate 35 by providing the latter with a central post -43- which passes through a hub -44- formed on the disk. The said post is provided in its upper end with a threaded socket for the reception of a screw 44 and the post projects above the hub of the plate so as to leave a small space between the screw-head and hub, whereby the disk 3 l is allowed a slight vertical play.

The lower face of the disk -S4- is provided with a pair of radially disposed lugs l5-45 which are adapted to normally engage correspondingly arranged recesses 45 i5 provided in the upper face of the plate 35. The lugs and recesses are rounded transversely so as to permit their disengagement when the operators foot is pressed against one of the arms i2 on the disk 34 to rotate the latter. To limit this rotary motion of the disk, I provide the latter with a lug 46 adapted to engage lugs -l7 l7- on the plate 35 as illustrated in Figs. 9 and 10 of the drawings.

The operation of the described dental-engine and controlling means will now be described. The powertransmission-wheel 11 is held normally over the central depression -7 of thefriction-disk 6 by the expansive force of the spiral-spring 16 on the shiftable shaft 10, and thus the wheel is out of contact with the disk, and at the same time the electric-switch 29 is held in position to cause its contact -30 to bear on the insulating block 28 in the contact-plate, to open the electric-circuit to cut out the motor. When the parts are in normal position, it will be understoodthat the foot-operated disk 34 is disposed with its lugs *4545 in engagement with the recesses 45 45 in the plate 35. This engagement serves to prevent accidental turning of the disk. When it is desired to use the dental-instrument, the operator applies the foot to one of the arms 42 on the disk 34* for the purpose of turning the disk, whereby the belt 3/' and wheel -33- are caused to turn the rock-shaft 20 to the left as viewed in Fig. 1 of the drawings. By this movement of the rock-shaft, the arm 19 and rod 1S- are actuated to shift the shaft 1 0 to the left in opposition to the spiral-spring, whereby the Wheel ll is carried correspondingly and caused to frictionally engage the disk 6 secured to the motor-shaft. Simultaneously with the movement of the wheel 1l into cngage ment with the disk -6, the electric-switch 2) is actuated by the said rock-shaft -20 so as to cause the electric-contact 30 to bear on the contact-plate -23- and thereby close the circuit. This closing of the electric-circuit obviously starts the motor -l and thus the disk 6 is caused to drive the wheel -11 and belt14 which is designed to transmit the power to the dental-instrument, (not shown), it being understood that the person using the instrument retains the foot against the arm 42 of the disk 34. If it is desired to increase the speed of the dental-instrument, the operator turns the floordisk 34 to a greater degree whereby the shaft 10- is shifted to carry the wheel 11 a further distance from the center of the friction-disk -6 so as to drive the wheel 11 faster, and thus the wheel and belt -14 are caused to transmit correspondingly increased speed to the instrument. By releasing the arm 42 of the disk -34 from pressure of the foot to a degree, the spiral-spring *l6 is allowed to exert expansive force on the shaft l0 whereby the latter is caused to be shifted in reverse direction and thus the wheel 11 is carried toward the center of the disk -6 to decrease the speed.

It will be apparent that the person using the dentalinstrument very easily and conveniently controls the transmission-mechanism so as to regulate the speed of the instrument.

When the arm -42- on the floor-disk 3 1 is released from the operators foot, the action of the spring l6 moves the wheel 11 out of operative relation with the disk G, i. e. to cause the wheel to stand over the central depression -7 in the disk -6 as shown in Figs. 1 and 4 of the drawings. This reverse movement of the shaft 10 causes the rod 18 and arm 19 to correspondingly turn the rock-shaft -20, whereby the electric-switch -29 is actuated to cause its contact -30 to bear on the insulating block 2S- secured to the plate 23. This bearing of the contact 30- on the block breaks the electric-circuit and thus cuts out the motor simultaneously with the throwing of the transmission-wheel -11 out of operative relation with the. disk 6 on the motorshait.

To adjust the motor-shaft 5 vertically to regulate the pressure of the friction-disk 6 on the transmission-wheel 11-, I employ a horizontally-disposed plate lS secured by means of screws i9i' 9- to the end of a hub -50 on the bottom of the motorcase, which plate is provided with a screw-threaded aperture 51 disposed axially in line with the shaft 5 and receives a screw 52 bearing against the lower end of the said shaft. By turning this screw 52 to the right, the shaft is lifted to carry the disk 6 toward the wheel -l1, and by turning the screw to the left, the shaft is allowed to drop by gravity whereby the pressure of the disk on the wheel is decreased.

The screw 52 is provided with a set-nut 53- for securely retaining the shaft in its adjusted position as clearly illustrated in Fig. 4 of the drawings.

What I claim as my invention isz- 1. In combination with an electric-motor and circuit therefor, a power-transmitting mechanism adapted to be thrown into and out of operative relation with the motor, and circuit-making and breaking means controlled by the said power-trausmittiug mechanism as and for the purpose set forth.

2. In combination with an electric-motor and circuit therefor. a power-transmitiing mechanism adapted to be thrown into and out of operative relation with the motor, a normally open switch in the electric-circuit, means con trolled by the power-transmitting mechanism for moving said switch to its closed position, and means for automatically moving the switch to its normal position as and for the purpose set forth.

3. In combination with an electrieanotor and circuit therefor, a variable-speed power-transmitting mechanism adapted to he thrown into and out of operative relation with the motor. and circuit-making and breaking means controlled by the power-transmitting mechanism as and for the purpose set forth.

4. In combination with an electric-motor and circuit therefor. a power-transmitting mechanism adapted to be thrown into and out of operative relation with the motor. a normally open switch connected to the eleetriecircuit, means controlled by the power-transmitting mechanism for closing the said switch when the mechanism is in its operative condition. and a spring adapted to actuate the switch-opera ting means to open the switch when the aforesaid mechanism is thrown out of operative relation with the motor as set forth.

3. In combination wan an electric-motor and circuit therefor, a variable-speed power-transmitting mechanism normally out of operative relation with the motor. a nor mally open switch in the electric-circuit. manually-open aicd means for throwing the power-transmitting mechanism into operative relation with the motor. means con trolled by the power-transmitting mechanism for closing the switch when the said mechanism is thrown into its operative condition, and a spring adapted to simultaneously throw said mechanism out of operative relation with the motor and move the switch to its normal position as set forth.

0. in a dcntatengine, the combination of an electricmotor having a suitable supply circuit, a power-transmit ting mechanism comprising an irrevoluble longitudinallyshiftable shaft and a wheel journaled on said shaft and adapted to be moved thereby into and out of operative relation with the motor. manually operated means for shift ing the shaft in one direction, means automatically shitting said shaft in opposite direction, a normally open cir cuit-maker and breaker in the electric-circuit and means actuated by the aforesaid shaft for operating said circuitnlaker and breaker as and for the purpose set forth.

7. In a dentahengine, the combination with an electricmotor having a suitable supply circuit and an inclosingcase, of a power-transmitting mechanism mounted on the motor-case, a circuit-making and breaking device supported on said motor-case. and means controlled by the powertransmitting mechanism for operating the circuit-making and breaking device as and for the purpose set forth.

8. In a dental-engine. the combination with an electricmotor having a supply circuit and an inclosing-case, of a power-transmitting mechanism mounted on the motor-case. a manually operated device connected to the transmission mechanism for varying the speed thereof. and for throw ing the same into operative relation with the motor, a normally open circuit'making and breaking switch connected to the circuit, means controlled by the manually operated device for moving said switch to its closed position, and automatic means for throwing the transmission-mcchauism out of. operative relation with the motor and simultani ously moving the switch to its normal position as set forth.

I). In a dental-engine, the combination with an electric motor having a supply-circuit and an inclosing-case. of a power-transmitting mechanism mounted on the motor-case and comprising an irrevoluble longitudinally-shiftable shaft and a wheel journaled on said shaft and driven by the motor, said wheel being normally out of operative relation with the motor, manually operated means for shifting the shaft in one direction to move the wheel into operative position, a spring adapted to shift said shaft in opposite direction to move the wheel to its normal position, a normally open switch connected to the electric-circuit. and means connecting the aforesaid shaft to the switch and operative for moving the switch to circuit-making and breaking position simultaneously with the movement of the transmission-wheel into and out of operative relation with the motor as set forth.

10. In a dental-engine, the combination with an electric motor and circuit therefor, of a power-transmitting mech anism comprising a wheel adapted to be shifted into and out of operative relation with the motor-shaft. shiftingmechanism including a rock-shaft. and a circuiiamaker and breaker actuated by said rock-shaft as set forth.

11. In a dental-engine, the combination with an electric- !notor and circuit therefor, of a powertransmitting mech anism comprising a wheel adapted to be shifted into and out of operative relation with the motor-shaft, shifting mechanism comprising a rockshaft. manually operated means for turning the rock-shaft, in one direction and automatically operating means for turning said shaft in reverse direction. and a normally open circuit-imikiug and breaking switch actuated by said rock-shaft as and for the purpose set forth.

12. In a dental-engine, the combination with an elect ic motor and circuit therefor, of a variable-speed powertransmitting mechanism. means for throwing said mcchair ism into operative relation with the motor. and comprising a rock-shaft connected to said mechanism, and circuitmaking and breaking means controlled by said rock-shaft as set forth.

In a dentabengine the combination with an electric motor and circuit therefor. of a variable-speed powershaft and moved into and out of engagement with the stationary contact simultaneously with the shifting of the aforesaid transmission into and out of operative relation with the motor as and for the purpose set forth.

14. In a dental-engine, the combination with an electricmotor and circuit therefor, of a variable-speed power transmitting-mechanism comprising an irrevoluble longitudinally-shiftable shaft and a wheel journaled on said shaft and adapted to be moved thereby into operative re lation with the motor-shaft, manually operated means ineluding a rock-shaft for shifting the aforesaid shaft in one direction, and automatic means for shifting the same in opposite direction, a lever connecting the rockshaft with the shiftable shaft, and a circuit-making and breaking switch fastened to said rock-shaft as and for the purpose set forth.

15. In a dental-engine, the combination with an electricmotor, of a powcr-transmitting mechanism, comprising a wheel and a belt driven thereby, manually operated means including a rockshaft and lever for moving said wheel into operative relation with the motor, spring-actuated means for automatically moving said wheel out of operative position, a stationary contactplate connected to the electric-circuit, and a circuit-making and breaking' mem ber fastened to the aforesaid rock-shaft and movable over said contact-plate as set forth.

16. In a dental-engine, the combination with an electricmotor and circuit therefor, of a variable-speed poweri'ransmitting mechanism, a foot-operated device for controlling said mechanism, and a circuit-maker and breaker connected to the foot-operated device as and for the pur pose set forth. v

17. In a dental-engine, the combination with an electric motor and circuit therefor, of a variable-speed powertransmitting mechanism, foot-operated devices including a rock-shaft for throwing said mechanism into operative relation with the motor, and spring'actuated means for automatically throwing the mechanism out of operative relation with said motor, an electriecontact connected to the circuit, and a switch in the circuit and fastened to the aforesaid rock-shaft, said switch being movable into engagement with the contact-plate by the action of the foot-operated devices and moved out of engagement with saidcontact-plate by the spring-actuated means as set forth.

18. In a dental-engine, the combination with an electricmotor and circuit therefor, of a power-transmitting mechanism comprising a shiftable wheel normally in inopera tive position in relation to said motor, a rockshait c0nnected to the said wheel, a pulley secured to said rockshaft, a foot-operated device, a belt connecting said foot 19. In a dental-engine, the combination with an electricmotor and its supply circuit and motor inclosing-cuse, of a mechanism comprising an irrevoluble longitudinallyshiftable shaft supported on the motorcase, a wheel journaled on said shaft, and a power-transmitting belt driven by said wheel, a spiral-spring surrounding said shaft and operative for holding the wheel normally out of operative relation with the motor-shaft, a rockshaft supported on the motor-case, a lever rigidly connected at one end to the rock-shaft, a rod pivotally connected to the free end of said lever and to the aforesaid shiftable shaft, a grooved wheel fastened to the said rock-shaft, a grooved wheel having a suitable floor-attachment, a belt connecting said grooved-wheels. flmtactuated means connected to the wheel on the floor and operative for turning the rock-shaft in one direction to shift the transmissiomwheel into operative relation with the motor-shaft, and a circuit-maker and breaker controlled by said rock-shaft as and for the pur pose set forth.

20. In a dental-engine, the combination with an electricmotor having an inclosingcase and a supply-circuit, of a bracket supported rigidly upon the motor-case, an irrevoluble horizontal shaft mounted longitudinally shiftable on said bracket, a wheel journaled on said shaft and adapted to be driven by the motor, manually-operated means for shifting the shaft in one direction to move the wheel into opera tive relation with the motor, a spring for automatically shifting said shaft in reverse direction to move the wheel out of operative position, a normally closed switch con nected to the electric-circuit and supported on the aforesaid bracket, and means actuated by the shiftable shaft for moving the switch to circuit-making and breaking posi tions as set forth.

21. In a dental-engine, the combination with an electricinotor having an inclosing-case, and a supply-circuit, of a bracket mounted upon the motorcase, and irrevoluble shaft supported longitudinally-shiftable on said bracket and provided at one end with a collar, a wheel journaled on said shaft and moved thereby into and out of operative relation with the motor, a rock-shaft journaled on the bracket and connected to the aforesaid shaft and adapted to shift the same in one direction to move the wheel into operative position, manually-operated means for actuating the rock-shaft, a spiral-spring surrounding the said shiftable shaft, and interposed between the collar thereon and the bracket, and serving to force the shaft in opposite direction to move the wheel out of operative position, a switch connected to the electric-circuit and actuated by the rockshaft, said switch being held normally in circuitbreaking position by the action of said spring, and moved to circuit-making position by the manually-operated means as set forth.

22. In a dental-engine, the combination with an electricmotor and circuit therefor, of a frictionally driven powertransmitting mechanism, manually operated means for throwing said mechanism into operative relation with the motor, means for automatically throwing said mechanism out of operative relation with the motor, a normally open circuit1naking and breaking switch connected to the electrio-circuit and moved to circuit-closing position by the manuall -operated means, and means controlled by the power nsnnt ing mechanism for automatically moving the switch to its normal position simultaneously with the .ihrowing of said mechanism out of operative relation with the motor as set forth.

23. A dental-engine comprising an electric-motor pro vided with an inclosing-case and having a suitable supplycircuit, a disk fastened to the motor-shaft, a shiftable power-transmission wheel supported on the motor-case and adapted to be driven by frictional engagement with said disk, means for moving said wheel into and out of contact with the disk, and circuit-making and breaking means arranged and operating in the manner set forth.

24. A dental-engine comprising an OleCtl'lCdllOiiOl havii g a suitable supply-circuit and provided with an inclosingcase, a variablospeed friction power-transmitting mech anism supported on the motor-case, manually-operatcd means for controlling said mechanism, and an electric-circuitanaker and breaker controlled by said manually operated means as set forth.

25. A dental-engine comprising an electricmotor having a supply-circuit, a disk secured to the shaft of the motor, an irrevoluble longitudinally-shittable shai't sup ported above the motor, a power-transmission wheel journaled on the latter shaft and shifted thereby and adapted to frictionally engage the aforesaid disk, said wheel being adapted to he moved radially in relation to the disk to vary the speed of the wheel and to be carried into and out of contact with the said disk, manually-operated means for shifting the said shaft in one direction, automatic means for shifting the shaft in reverse direction, an electric-switch connected to the circuit, mechanism actuated by the manually-operated means for moving the switch to circuit-making position, and actuated by the automatic means to move the same to circuit-breaking position as set forth.

20. In a dental-engine, the combination of an electricmotor provided with an inclosing-case and having its shaft disposed vertically,.a disk secured to the upper end of the 1 motor-shaft, a bracket supported upon the motor-case, a

horizontally disposed shaft mounted on the bracket and extending diametrically over the aforesaid disk, a powertransmission wheel mounted on the horizontal shaft and frictionally-driven by the aforesaid disk, said Wheel being adapted to be shifted radially in relation to the disk to vary the speed of the wheel, means for shifting the said wheel, and means for adjusting the disk in relation to the transmission-wheel as set forth.

27. In a dentalengine, the combination of an electricinotor having the longitudinally-adjustable shaft, a friction-disk fastened to said shaft, an irrevoluble longitudinally-shiftable shaft disposed at right angles to the motor shaft, and extending diametrically across the frictioirdisk, a power-transmission wheel journaled on the shiftable shaft and held, against longitudinal movement thereon, said \vheel being driven by frictional engagement with the disk, manually controlled means for shifting the latter shaft to move the wheel radially on the disk to vary the speed of the wheel, and means for adjusting the motorshal't to regulate the pressure of the disk on the transionavheel as set forth.

t. In a dental-engine, the combination of an electricmotor having a suitable supply-circuit and provided with an inclosing-easc, the motor-shaft being disposed vertically and having its upper end protruding from the case, a friction-disk secured to said end of the shaft, a bracket supported on top of the case and comprising a pair of upwardly extending arms provided with bearings disposed in horizontal alinement, an irrevoluble shaft mounted longitudinally shiftable in said bearings, a poWer-transmission \vheel journaled on the latter shaft and adapted to be driven by the said frictioirdisk, said \vheel being normally out 0f contact with the disk and moved by the shaft radially across the disk to vary the speed of the wheel, a rock-shaft supported on the aforesaid bracket, an arm and a groovedavheel rigidly fastened to the rock-shaft, a rod connecting said arm to the shiftable shaft, a foot-operated annular plate having a suitable pivotal connection with floor, a belt connecting said grooved-wheel and groovedplate and operative for moving the shiftable shaft in one direction, and a spring for automatically moving said shaft in reverse direction, a switch connected to the electric-circuit and fastened to the aforesaid rock-shaft as and for the purpose set forth.

WALLACE W. WILLIAMSON. Witnesses .I. .T. LAASS, G. Kaisnn, 

